This invention relates to a method of preparing multilayer metal/organic polymer composites. The multilayer composites have at least one thermoplastic organic polymer layer, a first metal layer adhered to at least one surface of the polymer layer and at least one additional metal layer adhered to the first metal layer. This invention also relates to the multilayer composites so prepared and to articles formed from such multilayer composites.
Metallized plastic articles have been prepared by applying a metal layer to a plastic material. Application of the metal layer has been accomplished by vacuum deposition, electrolytic or electroless deposition, foil lamination or similar metallizing techniques. Metallized plastic films so prepared have been used for decorative purposes because of properties such as flexibility and ability to be shaped to some extent to conform to various contours.
Unfortunately, the degree to which earlier versions of such metallized films or sheets or other articles can be shaped without rupture and/or separation of the metal from the polymer is limited. Accepted limitations include restricting localized dimensional changes to less than 25% in one direction and less than 20% in area.
Metallized films prepared in accordance with U.S. Pat. Nos. 4,115,619 and 4,211,822, the teachings of which are incorporated herein by reference thereto, are limited in terms of extensibility to an increase in area of at least 30%, preferably from about 50 to about 300%. A noticeable loss in both specular reflectance and optical density results at points of excessive elongation when such metallized films are stretched beyond the aforementioned limits. Even within said limits, a marked loss of optical density occurs when the metallized films are stretched at a forming temperature which exceeds the film's glass transition temperature, in degrees Kelvin, by 5 percent or more.
A formed article, where excessive stretching has taken place, has a marred appearance and diminished utility in decorative, electrical and packaging applications.
It would be desirable if there were available a process for preparing a multilayer, metal/organic polymer composite having at least two compositionally different metal alloy layers adhered to at least one surface of a thermoplastic organic polymer layer. Such a composite, after an increase in area of at least 30 percent, beneficially from about 50 to about 300 percent would desirably exhibit excellent specular reflectance, electroconductivity and barrier to vapor transmission.
It would also be desirable if the multilayer composite so produced had a high retention of optical density after being extended to an area which is at least 30 percent, desirably from about 50 to about 300 percent, greater than its original area. The multilayer composite has a high retention of optical density if it has an optical density, after extension, of at least 2, beneficially at least 3, and desirably at least 4.